/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.gson;

import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/**
 * A class representing an array type in Json. An array is a list of {@link JsonElement}s each of 
 * which can be of a different type. This is an ordered list, meaning that the order in which 
 * elements are added is preserved.  
 *  
 * @author Inderjeet Singh
 */
public final class JsonArray extends JsonElement implements Iterable<JsonElement> {
  private final List<JsonElement> elements;
  
  /**
   * Creates an empty JsonArray. 
   */
  public JsonArray() {
    elements  = new LinkedList<JsonElement>();
  }
  
  /**
   * Adds the specified element to self.
   * 
   * @param element the element that needs to be added to the array. 
   */
  public void add(JsonElement element) {
    elements.add(element);
  }
  
  /**
   * Adds all the elements of the specified array to self. 
   * 
   * @param array the array whose elements need to be added to the array. 
   */
  public void addAll(JsonArray array) {
    elements.addAll(array.elements);
  }

  /**
   * Reverses the elements of the array.
   */
  void reverse() {
    Collections.reverse(elements);
  }
  
  /**
   * Returns the number of elements in the array. 
   * 
   * @return the number of elements in the array.
   */
  public int size() {
    return elements.size();
  }

  /**
   * Returns an iterator to navigate the elemetns of the array. Since the array is an ordered list, 
   * the iterator navigates the elements in the order they were inserted. 
   * 
   * @return an iterator to navigate the elements of the array. 
   */
  public Iterator<JsonElement> iterator() {
    return elements.iterator();
  }
  
  /**
   * Returns the ith element of the array. 
   * 
   * @param i the index of the element that is being sought.
   * @return the element present at the ith index. 
   * @throws IndexOutOfBoundsException if i is negative or greater than or equal to the 
   * {@link #size()} of the array.
   */
  public JsonElement get(int i) {
    return elements.get(i);
  }
  
  /**
   * convenience method to get this array as a {@link Number} if it contains a single element.   
   *  
   * @return get this element as a number if it is single element array. 
   * @throws ClassCastException if the element in the array is of not a {@link JsonPrimitive} and 
   * is not a valid Number.  
   * @throws IllegalStateException if the array has more than one element. 
   */
  @Override 
  public Number getAsNumber() {
    if (elements.size() == 1) {
      return elements.get(0).getAsNumber();
    } 
    throw new IllegalStateException();
  }
  
  /**
   * convenience method to get this array as a {@link String} if it contains a single element.   
   *  
   * @return get this element as a String if it is single element array. 
   * @throws ClassCastException if the element in the array is of not a {@link JsonPrimitive} and 
   * is not a valid String.  
   * @throws IllegalStateException if the array has more than one element. 
   */
  @Override 
  public String getAsString() {
    if (elements.size() == 1) {
      return elements.get(0).getAsString();
    }
    throw new IllegalStateException();
  }
  
  /**
   * convenience method to get this array as a double if it contains a single element.   
   *  
   * @return get this element as a double if it is single element array. 
   * @throws ClassCastException if the element in the array is of not a {@link JsonPrimitive} and 
   * is not a valid double.  
   * @throws IllegalStateException if the array has more than one element. 
   */
  @Override 
  public double getAsDouble() {
    if (elements.size() == 1) {
      return elements.get(0).getAsDouble();
    }
    throw new IllegalStateException();
  }
  
  /**
   * convenience method to get this array as a float if it contains a single element.   
   *  
   * @return get this element as a float if it is single element array. 
   * @throws ClassCastException if the element in the array is of not a {@link JsonPrimitive} and 
   * is not a valid float.  
   * @throws IllegalStateException if the array has more than one element. 
   */
  @Override 
  public float getAsFloat() {
    if (elements.size() == 1) {
      return elements.get(0).getAsFloat();
    }
    throw new IllegalStateException();
  }
  
  /**
   * convenience method to get this array as a long if it contains a single element.   
   *  
   * @return get this element as a long if it is single element array. 
   * @throws ClassCastException if the element in the array is of not a {@link JsonPrimitive} and 
   * is not a valid long.  
   * @throws IllegalStateException if the array has more than one element. 
   */
  @Override 
  public long getAsLong() {
    if (elements.size() == 1) {
      return elements.get(0).getAsLong();
    }
    throw new IllegalStateException();
  }
  
  /**
   * convenience method to get this array as an integer if it contains a single element.   
   *  
   * @return get this element as an integer if it is single element array. 
   * @throws ClassCastException if the element in the array is of not a {@link JsonPrimitive} and 
   * is not a valid integer.  
   * @throws IllegalStateException if the array has more than one element. 
   */
  @Override 
  public int getAsInt() {
    if (elements.size() == 1) {
      return elements.get(0).getAsInt();
    }
    throw new IllegalStateException();
  }
  
  /**
   * convenience method to get this array as a primitive short if it contains a single element.   
   *  
   * @return get this element as a primitive short if it is single element array. 
   * @throws ClassCastException if the element in the array is of not a {@link JsonPrimitive} and 
   * is not a valid short.  
   * @throws IllegalStateException if the array has more than one element. 
   */
  @Override 
  public short getAsShort() {
    if (elements.size() == 1) {
      return elements.get(0).getAsShort();
    }
    throw new IllegalStateException();
  }
  
  /**
   * convenience method to get this array as a boolean if it contains a single element.   
   *  
   * @return get this element as a boolean if it is single element array. 
   * @throws ClassCastException if the element in the array is of not a {@link JsonPrimitive} and 
   * is not a valid boolean.  
   * @throws IllegalStateException if the array has more than one element. 
   */
  @Override 
  public boolean getAsBoolean() {
    if (elements.size() == 1) {
      return elements.get(0).getAsBoolean();
    }
    throw new IllegalStateException();
  }
  
  /**
   * convenience method to get this array as an Object if it contains a single element.   
   *  
   * @return get this element as an Object if it is single element array. 
   * @throws ClassCastException if the element in the array is of not a {@link JsonPrimitive} and 
   * is not a valid Object.  
   * @throws IllegalStateException if the array has more than one element. 
   */
  @Override 
  Object getAsObject() {
    if (elements.size() == 1) {
      return elements.get(0).getAsObject();
    }
    throw new IllegalStateException();
  }

  @Override
  protected void toString(StringBuilder sb) {
    sb.append('[');
    boolean first = true;
    for (JsonElement element : elements) {
      if (first) {
        first = false;
      } else {
        sb.append(',');
      }      
      element.toString(sb);
    }
    sb.append(']');
  }
}
